It would help to see a picture of the 2 pieces, to know what you are trying to match. You should be able to fudge one or the other, but I don't know the pattern.
As for all those "perfect" quilts you see - that is the beauty of someone else's work. You never see the flaws anywhere but your own. I'm sure even the quilts you think are gorgeous, the maker probably thought there was some flaw somewhere. We are always most critical of our own work - and of course you *know* where the issue is. In a finished quilt, I'm sure that even if you don't get this one spot to match perfectly, no one but you is every likely to notice it.